Orthogonal frequency division multiplexing access (OFDMA) or its variant; which are orthogonal frequency division multiplexing (OFDM) based technique is adopted in recent wireless systems for multiple accesses in the downlink (DL) and/or uplink (UL) to provide broadband connectivity to users. It is due to its ability to exploit frequency diversity using multi user scheduling along with forward error correcting code (FEC), and also ease of implementation using computationally efficient IFFT/FFT modules. Moreover, OFDM systems can also be scaled to multiple input, multiple output (MIMO) systems with any number of antennas both at the transmitter and receiver. The main goal of the existing cellular technologies is to serve broadband data to the users in a spectrally efficient manner, and also to provide higher data rate to the users. Long term evolution advanced (LTE-A), which is also an OFDM based MIMO system, and it supports only a fixed subcarrier spacing of 15 KHz for its data transmission to the users.
Due to the exponential growth in the data rate requirement there is a need to support larger bandwidth transmission. Also simultaneously, there is a need for supporting power efficient low bit rate transmissions due to the recent development in the Internet of things (IoT). Moreover, there is a requirement of the ensuing technology to meet conflicting requirements like simultaneous support of low and high data rate, high and low latency reliable communication using an unified design.
A new radio access technology (NRAT) is being designed for the 5th generation (5G) system and is expected to support multiple requirements using the same technology. Different services like enhanced mobile broadband (eMBB), ultra-reliable low latency communication (URLLC), enhanced machine type communication (eMTC) etc., are expected to be supported within a single component carrier bandwidth. The 3GPP group currently focuses on defining a new waveform for the 5G technology, for providing better spectral localization, low PAPR, and higher spectral efficiency. Many waveforms including filter bank multi carrier (FBMC), generalized frequency division multiplexing (GFDM), universal filtered multicarrier (UFMC), variants of the OFDM, and discrete Fourier transform-spread-OFDM (DFT-S-OFDM) with windowing or filtering are being considered as possible candidate for the new waveform for the 5G technology.
The main challenge of the NRAT in supporting the different services is to serve them using a unified frame structure with a single waveform. Also, it should support different subcarrier spacing across smaller subbands of a single larger component carrier bandwidth. Each subcarrier spacing corresponds to certain numerology. The bands corresponding to different numerology experience different channel conditions, and therefore, the effective symbol duration and other requirements like cyclic prefix (CP) or related variants like guard period or guard band are different for different numerologies. Co-existence of different numerologies creates inter-carrier interference (ICI) and in turn inter-numerology interference (INI) due to different subcarrier spacing and different CP requirements.
The above information is presented as background information only to help the reader to understand the present invention. Applicants have made no determination and make no assertion as to whether any of the above might be applicable as Prior Art with regard to the present application.